This invention relates to safety devices for controlling the flow of fuel to internal combustion engines so as to protect an engine against damage due to insufficient oil pressure in the lubricating system thereof or to overheating, and more particularly to protective apparatus for use with gasoline or diesel engines which drive motor vehicles.
There are in the prior art a number of engine protective devices which completely shut off the flow of fuel to the engine in the event of inadequate lubricating oil pressure or overheating, including those disclosed in U.S. Pat. Nos. 3,202,143 and 3,590,798, on which the device of the present invention is an improvement.
The device of U.S. Pat. No. 3,202,143, dated Aug. 24, 1965, is a full fuel shut-off valve effecting an automatic full shut-down of the engine when the oil pressure drops below a predetermined value or the engine overheats, but it also includes a manually operable override which, when operated, will allow sufficient fuel to reach the engine to produce maximum power and speed even though the oil pressure has dropped below normal, or the engine is overheated, with possible consequent damage to the engine.
U.S. Pat. No. 3,590,798, dated July 6, 1971, also discloses an engine safety device responsive to abnormal oil pressure and coolant temperature conditions, but this device is not a full fuel shut-off effecting a full shut-down of the engine, but is an automatic engine decelerating or detorqueing valve by virtue of a built-in fuel by-pass that continues to supply the engine with a restricted quantity of fuel after the main fuel valve is closed. It also includes a manually operated override which, when operated, permits operation of the engine at maximum power and speed, as in the case of the device of U.S. Pat. No. 3,202,143.
It is therefore the object of the present invention to improve upon the engine shut-down devices of the prior art, particularly those of U.S. Pat. Nos. 3,202,143 and 3,590,798, by providing a full fuel shut-off effecting a full shut-down of the engine when abnormal pressure or temperature conditions arise, and a restricted manual override which will minimize or prohibit abuse of a failing engine by disallowing maximum power and speed after the automatic shut-down. This improvement is particularly beneficial in vehicular applications wherein, after automatic shut-down, the driver of the vehicle gets out, engages the manual override, and restarts the engine, but cannot move the vehicle and its load except at slow speed and low gear.